The enigma of ifosfamide encephalopathy

Ifosfamide - History, efficacy, toxicity and encephalopathy

In this review we trace the passage of fundamental ideas through 20^th century cancer research that began with observations on mustard gas toxicity in World War I. The transmutation of these ideas across scientific and national boundaries, was channeled from chemical carcinogenesis labs in London via Yale and Chicago, then ultimately to the pharmaceutical industry in Bielefeld, Germany. These first efforts to checkmate cancer with chemicals led eventually to the creation of one of the most successful groups of cancer chemotherapeutic drugs, the oxazaphosphorines, first cyclophosphamide (CP) in 1958 and soon thereafter its isomer ifosfamide (IFO). The giant contributions of Professor Sir Alexander Haddow, Dr. Alfred Z. Gilman & Dr. Louis S. Goodman, Dr. George Gomori and Dr. Norbert Brock step by step led to this breakthrough in cancer chemotherapy. A developing understanding of the metabolic disposition of ifosfamide directed efforts to ameliorate its side-effects, in particular, ifosfamide-induced encephalopathy (IIE). This has resulted in several candidates for the encephalopathic metabolite, including 2-chloroacetaldehyde, 2-chloroacetic acid, acrolein, 3-hydroxypropionic acid and S-carboxymethyl-L-cysteine. The pros and cons for each of these, together with other IFO metabolites, are discussed in detail. It is concluded that IFO produces encephalopathy in susceptible patients, but CP does not, by a "perfect storm," involving all of these five metabolites. Methylene blue (MB) administration appears to be generally effective in the prevention and treatment of IIE, in all probability by the inhibition of monoamine oxidase in brain potentiating serotonin levels that modulate the effects of IFO on GABAergic and glutamatergic systems. This review represents the authors' analysis of a large body of published research.

Methylene blue and ifosfamide-induced encephalopathy: Myth or reality?

BACKGROUND

Ifosfamide-induced encephalopathy (IIE) is a rare and serious adverse reaction. Thus far, no standard medication has been documentedto be efficient in the reversal of IIE, and while ifosfamide infusion interruption and hydration are recommended, methylene blue (MB) administration remains controversial.

METHODS

We retrospectively reviewed medical records to assess cases with IIE after ifosfamide infusion. We included all patients having received an ifosfamide infusion during their hospitalization in the medical oncology unit of the National Institute of Oncology in Rabat, Morocco, between September 2016 and September 2017. We subsequently conducted a literature review to determine the role of MB in IIE by searching PubMed using the terms "Methylene Blue" and "Ifosfamide".

RESULTS

A total of 88 patients received ifosfamide, and four patients had IIE. Ifosfamide infusion was stopped immediately after the IIE occurrence, and patients underwent renal function correction with hydration. All patients received MB infusion, and three patients had an improvement of their neurological status. As regards the literature review, 34 articles were reviewed and 16 items were included in the review. Overall, 38 (65.5%) patients received MB infusion and 28 (75.6%) patients responded favorably to the treatment.

CONCLUSIONS

Methylene blue can be used as a treatment for IIE owing to the severity of the IIE as well as absence of standard medication. Nonetheless, side effects such as serotonergic syndrome should be investigated. More broadly, prospective studies and controlled trials are needed to explore the contribution of MB in IIE management and encourage its use.

Liquid formulation of ifosfamide increased risk of encephalopathy: A case-control study in a pediatric population

BACKGROUND

Several clusters of encephalopathy occurred after the market change from Holoxan® (ifosfamide lyophilized powder) to Ifosfamide EG® (liquid formulation) and justified a formal survey in 2015. In June 2016, the regulatory authority decided to apply a precautionary measure in reducing the shelf life of Ifosfamide EG® at 7 months. One-year study from spontaneous reports lead to suspect a potential residual risk. Due to the many limitations associated with spontaneous notifications, we performed a multicentric observational study, aiming to better explore this pharmacovigilance signal.

METHODS

We performed a case-control study in pediatric oncology Departments of 25 university hospitals between July 1st, 2016 and July 1st, 2018. All children (<18 y.o.) receiving liquid formulation or lyophilized powder formulation during the study period were included. Patients with at least one occurrence of encephalopathy were considered as cases. Logistic regression model was used to estimate the odds ratio of encephalopathy between exposure groups.

RESULTS

During the study period, 52 cases and 495 controls were included. A residual over-risk of encephalopathy was associated with ifosfamide 7-month shelf-life liquid formulation compared to lyophilized powder (adjusted OR 1.91, 95% CI: 1.03-3.53).

CONCLUSIONS

Observed difference does not seem to be related to the pathology treated, the doses used, the co-medications, a meningeal localization and/or an irradiation of the central nervous system. This study confirms data from spontaneous reports that led to the precautionary measure for the liquid formulation. Even if the risk of encephalopathy seems reduced, our study suggests the persistence of a residual risk of encephalopathy associated with liquid formulation compared to the lyophilized powder.

Ifosfamide Encephalopathy: A Case Report

The aim of this short communication is to discuss the mechanism, modality and treatment of ifosfamide encephalopathy. We present the case of a 52-year-old woman treated with this alkylating agent who developed severe neurotoxicity. It was resolved with administration of Methylene blue, abundant intravenous hydration and interruption of ifosfamide.

Two Episodes of Ifosfamide-Related Neurotoxicity in the Same Patient following Different Schedules and Doses of the Drug. A Case Report

We report the first case of recurrent ifosfamide-related neurotoxicity in the same patient following two distinct administrations of the drug at different doses and schedules and with a long interval between the two episodes. Remarkably, the first event was characterized by confusion and hallucinations, while the second, 29 months later, was characterized by partial and generalized seizures. Between the two episodes the patient had received high-dose cyclophosphamide, an oxazophoshorine agent closely related to ifosfamide, without any neurological side effects. We briefly discuss the diagnosis and management of ifosfamide-related encephalopathy.

Prenatal effects of transplacental exposure to ifosfamide in rats

Ifosfamide is an alkylating chemotherapeutic agent that exhibits activity against a wide range of tumors. Exposure to such agent just prior to mating (preconception period) may have adverse effects on developing embryos. I investigated the rate of apoptosis and the histological changes in both placenta and developing fetal tissues after exposure to ifosfamide of young female rats before mating. I clarified the roles of the drug and the placenta in causing fetal developmental toxicity. Rats were divided into four groups: (1) untreated controls, (2) rats administered saline, (3 and 4) rats administered 25 mg/kg and 50 mg/kg ifosfamide, respectively. After treatment of females with ifosfamide, the treated females were allowed to mate with normal untreated males. All pregnant animals were sacrificed on day 18 of gestation. Treatment with high doses of ifosfamide caused small placentas, fewer viable fetuses, greater post-implantation losses and more resorbed fetuses. Reduced progesterone and increased prolactin levels also were found. Immunohistochemical staining, the TUNEL technique and histological studies showed increased apoptotic cells and many histological changes in the placenta, and in fetal brain, liver and kidney tissues. Ifosfamide treatment increased apoptosis and caused hypoplasia of placental basal and labyrinth zones, which resulted in pathological changes in developing fetal tissue.

Investigation of ifosfamide and chloroacetaldehyde renal toxicity through integration of in vitro liver-kidney microfluidic data and pharmacokinetic-system biology models

We have integrated in vitro and in silico data to describe the toxicity of chloroacetaldehyde (CAA) on renal cells via its production from the metabolism of ifosfamide (IFO) by hepatic cells. A pharmacokinetic (PK) model described the production of CAA by the hepatocytes and its transport to the renal cells. A system biology model was coupled to the PK model to describe the production of reactive oxygen species (ROS) induced by CAA in the renal cells. In response to the ROS production, the metabolism of glutathione (GSH) and its depletion were modeled by the action of an NFE2L2 gene-dependent pathway. The model parameters were estimated in a Bayesian context via Markov Chain Monte Carlo (MCMC) simulations based on microfluidic experiments and literature in vitro data. Hepatic IFO and CAA in vitro intrinsic clearances were estimated to be 1.85 x 10(-9) μL s(-1) cell(-1) and 0.185 x 10(-9) μL s(-1) cell(-1) ,respectively (corresponding to an in vivo intrinsic IFO clearance estimate of 1.23 l h(-1) , to be compared to IFO published values ranging from 3 to 10 l h(-1) ). After model calibration, simulations made at therapeutic doses of IFO showed CAA renal intracellular concentrations ranging from 11 to 131 μM. Intracellular CAA concentrations above 70 μM induced intense ROS production and GSH depletion. Those responses were time and dose dependent, showing transient and non-linear kinetics. Those results are in agreement with literature data reporting that intracellular CAA toxic concentrations range from 35 to 320 μM, after therapeutic ifosfamide dosing. The results were also consistent with in vitro CAA renal cytotoxicity data.

Acrolein and chloroacetaldehyde: an examination of the cell and cell-free biomarkers of toxicity

Cyclophosphamide and ifosfamide are two commonly used DNA-alkylating agents in cancer chemotherapy that undergo biotransformation to several toxic and non-toxic metabolites, including acrolein and chloroacetaldehyde (CAA). Acrolein and CAA toxicities occur by several different mechanisms, including ROS formation and protein damage (oxidation), however, these pathways of toxicity and protecting agents used to prevent them have yet to be compared and ranked in a single study. This research focused on the molecular targets of acrolein and CAA toxicities and strategies to decrease toxicities. Hepatocyte viability (cytotoxicity) was assessed using Trypan blue uptake; formation of reactive oxygen species (ROS) and endogenous H2O2 were also assessed in the hepatocyte model. In cell-free models (bovine serum albumin and hepatic microsomes), protein carbonylation was the measurement of toxicity. The present study demonstrated that acrolein was a more potent toxin than CAA for freshly isolated rat hepatocytes, bovine serum albumin and rat hepatic microsomes. Acrolein protein carbonylation was dependent on its concentration; as acrolein concentration increased, protein carbonylation increased in a linear trend, whereas, CAA deviated from the trend and did not cause protein carbonylation at lower concentrations (<400 μM). Aldehyde dehydrogenase (ALDH) is a major pathway for detoxifying pathway for CAA in hepatocytes, as a 3-fold increase in cytotoxicity occurred when cells were incubated with cyanamide, an ALDH inhibitor. Inhibiting ALDH or depleting GSH in hepatocytes increased cytotoxicity by about 3-fold in acrolein-treated hepatocytes. The overall effectiveness of protecting agents to prevent or suppress acrolein or CAA toxicities in cell and cell-free models were ranked in order of most effective to least effective: reducing agents (sodium borohydride, sodium bisulfite)>thiol-containing compounds (N-acetylcysteine, cysteine, glutathione, 2-mercaptoethane sulfonate [MESNA], penicillamine)>carbonyl scavengers/amines (aminoguanidine, hydralazine, hydroxylamine)>antioxidants/ROS scavengers (ascorbic acid, Trolox; only utilized in hepatocyte system). An understanding of acrolein and CAA toxicities and the ability of protecting agents to protect against toxicities may help to establish or improve existing therapeutic interventions against the side effects associated with acrolein or CAA in cyclophosphamide or ifosfamide treatment.

Investigation of ifosfamide nephrotoxicity induced in a liver-kidney co-culture biochip

In this article, we present a liver-kidney co-culture model in a micro fluidic biochip. The liver was modeled using HepG2/C3a and HepaRG cell lines and the kidney using MDCK cell lines. To demonstrate the synergic interaction between both organs, we investigated the effect of ifosfamide, an anticancerous drug. Ifosfamide is a prodrug which is metabolized by the liver to isophosforamide mustard, an active metabolite. This metabolism process also leads to the formation of chloroacetaldehyde, a nephrotoxic metabolite and acrolein a urotoxic one. In the biochips of MDCK cultures, we did not detect any nephrotoxic effects after 72 h of 50 µM ifosfamide exposure. However, in the liver-kidney biochips, the same 72 h exposure leads to a nephrotoxicity illustrated by a reduction of the number of MDCK cells (up to 30% in the HepaRG-MDCK) when compared to untreated co-cultures or treated MDCK monocultures. The reduction of the MDCK cell number was not related to a modification of the cell cycle repartition in ifosfamide treated cases when compared to controls. The ifosfamide biotransformation into 3-dechloroethylifosfamide, an equimolar byproduct of the chloroacetaldehyde production, was detected by mass spectrometry at a rate of apparition of 0.3 ± 0.1 and 1.1 ± 0.3 pg/h/biochips in HepaRG monocultures and HepaRG-MDCK co-cultures respectively. Any metabolite was detected in HepG2/C3a cultures. Furthermore, the ifosfamide treatment in HepaRG-MDCK co-culture system triggered an increase in the intracellular calcium release in MDCK cells on contrary to the treatment on MDCK monocultures. As 3-dechloroethylifosfamide is not toxic, we have tested the effect of equimolar choloroacetaldehyde concentration onto the MDCK cells. At this concentration, we found a quite similar calcium perturbation and MDCK nephrotoxicity via a reduction of 30% of final cell numbers such as in the ifosfamide HepaRG-MDCK co-culture experiments. Our results suggest that ifosfamide nephrotoxicity in a liver-kidney micro fluidic co-culture model using HepaRG-MDCK cells is induced by the metabolism of ifosfamide into chloroacetaldehyde whereas this pathway is not functional in HepG2/C3a-MDCK model. This study demonstrates the interest in the development of systemic organ-organ interactions using micro fluidic biochips. It also illustrated their potential in future predictive toxicity model using in vitro models as alternative methods.

Ifosfamide Encephalopathy

Encephalopathy is a potentially fatal toxicity of ifosfamide. Clinical manifestations of encephalopathy range from fatigue and confusion to coma and death. Early identification of this toxicity and prompt cessation of ifosfamide are the essential elements in the management of ifosfamide encephalopathy. Accurate prediction of this toxicity is often difficult. Based on the limited available evidence, methylene blue, an electron acceptor, may have a role in the treatment and the prevention of neurotoxicity. This paper reviews the current understanding of ifosfamide encephalopathy.

Encéphalopathie induite par l'ifosfamide : 15 observations

INTRODUCTION

Ifosfamide is an alkylating agent used in the treatment of germ-cell tumors, sarcomas and lymphomas. One of its main side effects is the encephalopathy of which the incidence may reach 30% in the literature, in adults and children just as well.

OBJECTIVES

Based on both our experience and a review of the literature, we propose some recommendations for the management of this complication.

PATIENTS AND METHODS

We report 15 encephalopathy cases in non-brain tumor patients, which occurred between January 1987 and March 2002 in children from 2 to 17 years old, treated for solid tumors at the Institut Gustave Roussy. Ifosfamide was administered at a posology between 5.4 and 15 g/m(2)/course, associated with other antimitotics such as actinomycin D, etoposide or vincristine.

RESULTS

Six patients experienced a grade III neurological toxicity according to the NCI classification, which developed as excess drowsiness lasting up to 36 hours. Six other patients developed grade IV neurotoxicity, including two comas resolving within 4 days and four short generalized convulsions. Three other children experienced grade II drowsiness. Brain MRIs were normal and EEG showed an aspecific encephalopathy tracing. This early central neurotoxicity appeared right from the first administration, and occurred immediately after the first injection or during the second or third day of treatment. It was most often reversible, usually 3 to 5 days after the last ifosfamide administration. Five patients were administered a treatment with Methylene Blue with a demonstrable efficacy in only one case. No death or neurological sequelae have been noted. Ifosfamide has been renewed after the neurological accident in 7 of those patients. Only 1 of those 7 patients developed grade IV neurotoxicity during the next course of treatment. In 2 of those 7 children, Methylene Blue was used in a prophylactic way. No neurological disorders have been noted during the next courses of treatment.

DISCUSSION

In the literature, the following are described as risk factors for ifosfamide encephalopathy: advanced pelvic disease, previous cisplatyl treatment and renal failure. We have not found any of these predisposing factors in our series, but three of the fifteen patients had severe neurotoxicity associated with Vincristin during previous treatments.

CONCLUSION

Facing a clinical diagnosis of ifosfamide encephalopathy, it is recommended to discontinue administration of ifosfamide and inject by intravenous route 50 mg Methylene Blue every 4 hours until the symptomatology recedes. The re-challenge of Ifosfamide is not contra-indicated and should be performed under prophylactic treatment with Methylene Blue by intravenous route at the dose of 50 mg every 6 hours.

Efficacy and tolerability of the ifosfamide-epirubicin combination in relapsed ovarian cancer

A retrospective study evaluating the efficacy and tolerability of epirubicin-ifosfamide (EI) in patients with relapsed advanced ovarian cancer (ROC) after prior chemotherapy was conducted. A total of 93 patients received epirubicin (50 mg/m(2), day 1), ifosfamide (1500 or 2500 mg/m(2), days 1-3), and mesna monthly. Thirty-five percent had received one line of chemotherapy (platinum 100%, taxanes 8%); 38%, two lines; and 27%, more than two lines. Fifty-three percent received 2500 mg/m(2)/day ifosfamide and 47% received 1500 mg/m(2)/day ifosfamide. Ifosfamide was administered by continuous infusion in 12 patients. Mean number of courses was 4 (1-12). Grade 4 toxicity was 69% neutropenia and 12% thrombocytopenia. Three patients on high-dose ifosfamide as a short infusion had central nervous system dysfunction resulting in death. There were 84 assessable patients: 7 (8%), complete responses; 13 (15%), partial responses; and 20 (24%), stable disease. Median time to progression was 5 months (3 days to 36 months). The EI combination appears to be effective in ROC. However, toxicity with high-dose ifosfamide administered by short infusion is not acceptable. Tolerability can be improved using ifosfamide at 1500 mg/m(2) by continuous infusion. The combination of ifosfamide with newer anthracycline agents such as liposomal doxorubicin may be an alternative and needs further evaluation for use after first-line taxane-based chemotherapy.

Phase I and pharmacokinetic study of the combination of topotecan and ifosfamide administered intravenously every 3 weeks

To determine the maximum-tolerated dose (MTD), dose-limiting toxicities, and pharmacokinetics of topotecan administered as a 30-min intravenous (i.v.) infusion over 5 days in combination with a 1-h i.v. infusion of ifosfamide (IF) for 3 consecutive days every 3 weeks. Patients with advanced malignancies refractory to standard therapy were entered into the study. The starting dose of topotecan was 0.4 mg m⁻² day⁻¹ × 5 days. Ifosfamide was administered at a fixed dose of 1.2 g m⁻² day⁻¹ × 3 days. In all, 36 patients received 144 treatment courses. Owing to toxicities, the schedule of topotecan administration was reduced from 5 to 3 days. The MTD was reached at topotecan 1.2 mg m⁻² day⁻¹ × 3 days with IF 1.2 g m⁻² day⁻¹ × 3 days. Haematological toxicities were dose limiting. Neutropenia was the major toxicity. Thrombocytopenia and anaemia were rare. Nonhaematological toxicities were relatively mild. Partial responses were documented in three patients with ovarian cancer dosed below the MTD. Topotecan and IF did not appear to interact pharmacokinetically. The relationships between the exposure to topotecan lactone and total topotecan, and the decrease in absolute neutrophil count and the decrease in thrombocytes, were described with sigmoidal–E_max models. The combination of 1.0 mg m⁻² day⁻¹ topotecan administered as a 30-min i.v. infusion daily times three with 1.2 g m⁻² day⁻¹ IF administered as a 1-h i.v. infusion daily times three every 3 weeks was feasible. However, the combination schedule of topotecan and IF did result in considerable haematological toxicity and in conjunction with previously reported pronounced nonhaematological toxicities and treatment related deaths, it may be concluded that this is not a favourable combination.

Ifosfamide and vinorelbine in advanced platinum-resistant ovarian cancer: excessive toxicity with a potentially active regimen

OBJECTIVES

The aim of this study was to determine the activity and toxicity of a vinorelbine and ifosfamide combination in platinum-resistant advanced ovarian cancer.

PATIENTS AND METHODS

Patients were treated with ifosfamide (2 g/m(2)/day) infused over 1 h x 3 days (with mesna uroprotection) and vinorelbine (30 mg/m(2)) on days 1 and 8. Treatment was repeated on a 21-day schedule. In order to avoid unacceptable toxicity in this subset of patients where the chemotherapy is mainly palliative, the Bryant and Day two-stage phase II trial design incorporating toxicity considerations was chosen. A cutoff point for the response rate (10%) and for severe toxicity (25%) was established for the first 14 patients.

RESULTS

Between February 1997 and December 1998, 11 paclitaxel and platinum-resistant patients and 1 potentially platinum-sensitive patient were treated. Five patients (41%) experienced grade 3-4 central nervous toxicity requiring hospital admission. In accordance with the Bryant and Day design, the study was stopped early because greater than 25% of the first 14 patients developed grade 3-4 neurotoxicity. A retrospective review of clinical characteristics of these patients showed at least one well-known risk factor associated with ifosfamide central toxicity. Hematological toxicity was common, mainly grade 4 neutropenia, which was observed in all but 1 patient, usually of short duration, and there were 4 episodes of neutropenic fever. Ten patients were evaluated for response. Two complete responses and 1 partial response according to CA-125 criteria were observed.

CONCLUSION

This combination may be active in platinum-resistant ovarian cancer but the high toxicity encountered, principally neurotoxicity in those with large central pelvic masses, means that further studies with this schedule may not be warranted.

Population pharmacokinetics of ifosfamide and its dechloroethylated and hydroxylated metabolites in children with malignant disease: a sparse sampling approach

OBJECTIVE

To assess the feasibility of a sparse sampling approach for the determination of the population pharmacokinetics of ifosfamide, 2- and 3-dechloroethyl-ifosfamide and 4-hydroxy-ifosfamide in children treated with single-agent ifosfamide against various malignant tumours.

DESIGN

Pharmacokinetic assessment followed by model fitting.

PATIENTS

The analysis included 32 patients aged between 1 and 18 years receiving a total of 45 courses of ifosfamide 1.2, 2 or 3 g/m2 in 1 or 3 hours on 1, 2 or 3 days.

METHODS

A total of 133 blood samples (median of 3 per patient) were collected. Plasma concentrations of ifosfamide and its dechloroethylated metabolites were determined by gas chromatography. Plasma concentrations of 4-hydroxy-ifosfamide were measured by high-performance liquid chromatography. The models were fitted to the data using a nonlinear mixed effects model as implemented in the NONMEM program. A cross-validation was performed.

RESULTS

Population values (mean +/- standard error) for the initial clearance and volume of distribution of ifosfamide were estimated at 2.36 +/- 0.33 L/h/m2 and 20.6 +/- 1.6 L/m2 with an interindividual variability of 43 and 32%, respectively. The enzyme induction constant was estimated at 0.0493 +/- 0.0104 L/h2/m2. The ratio of the fraction of ifosfamide metabolised to each metabolite to the volume of distribution of that metabolite, and the elimination rate constant, of 2- and 3-dechloroethyl-ifosfamide and 4-hydroxy-ifosfamide were 0.0976 +/- 0.0556, 0.0328 +/- 0.0102 and 0.0230 +/- 0.0083 m2/L and 3.64 +/- 2.04, 0.445 +/- 0.174 and 7.67 +/- 2.87 h(-1), respectively. Interindividual variability of the first parameter was 23, 34 and 53%, respectively. Cross-validation indicated no bias and minor imprecision (12.5 +/- 5.1%) for 4-hydroxy-ifosfamide only.

CONCLUSIONS

We have developed and validated a model to estimate ifosfamide and metabolite concentrations in a paediatric population by using sparse sampling.

Clinical pharmacokinetics and pharmacodynamics of ifosfamide and its metabolites

This review discusses several issues in the clinical pharmacology of the antitumour agent ifosfamide and its metabolites. Ifosfamide is effective in a large number of malignant diseases. Its use, however, can be accompanied by haematological toxicity, neurotoxicity and nephrotoxicity. Since its development in the middle of the 1960s, most of the extensive metabolism of ifosfamide has been elucidated. Identification of specific isoenzymes responsible for ifosfamide metabolism may lead to an improved efficacy/toxicity ratio by modulation of the metabolic pathways. Whether ifosfamide is specifically transported by erythrocytes and which activated ifosfamide metabolites play a key role in this transport is currently being debated. In most clinical pharmacokinetic studies, the phenomenon of autoinduction has been observed, but the mechanism is not completely understood. Assessment of the pharmacokinetics of ifosfamide and metabolites has long been impaired by the lack of reliable bioanalytical assays. The recent development of improved bioanalytical assays has changed this dramatically, allowing extensive pharmacokinetic assessment, identifying key issues such as population differences in pharmacokinetic parameters, differences in elimination dependent upon route and schedule of administration, implications of the chirality of the drug and interpatient pharmacokinetic variability. The mechanisms of action of cytotoxicity, neurotoxicity, urotoxicity and nephrotoxicity have been pivotal issues in the assessment of the pharmacodynamics of ifosfamide. Correlations between the new insights into ifosfamide metabolism, pharmacokinetics and pharmacodynamics will rationalise the further development of therapeutic drug monitoring and dose individualisation of ifosfamide treatment.

Determination of ifosfamide, 2- and 3-dechloroethyifosfamide using gas chromatography with nitrogen-phosphorus or mass spectrometry detection

A comparison was made between methods for determining ifosfamide (IF), 2- (2DCE) and 3-dechloroethylifosfamide (3DCE) using gas chromatography with nitrogen-phosphorus detection (GC-NPD) versus positive ion electron-impact ion-trap mass spectrometry (GC-MS2). Sample pretreatment involved liquid-liquid extraction with ethyl acetate after adding trofosfamide as internal standard and alkalinization. The GC-NPD was linear, specific, and sensitive for all analytes in the range of 0.0500-100 microg/mL with lower limits of quantification (LLQ) of 0.0500 microg/mL using a 50-microgL plasma sample. The GC-MS2 was linear, specific, and sensitive for IF, 2DCE, and 3DCE in the ranges of 0.250-100, 0.500-25.0, and 0.500-25.0 microg/mL, respectively, with LLQs of 0.250, 0.500, and 0.500 microg/mL. The ranges of accuracy, within-day precision, and between-day precision for analysis of all compounds with GC-NPD did not exceed 93.3% to 105.4%, 8.0% and 9.8%, respectively. The ranges of accuracy, within-day precision, and between-day precision for analysis of all compounds with GC-MS2 did not exceed 86.5% to 99.0%, 9.0% and 12.7%, respectively. In conclusion, GC-NPD proved to be superior to GC-MS2 in sensitivity, detection range, accuracy, and precisions. Therefore GC-NPD is the method of choice for fast un-derivatized determination of IF, 2DCE, and 3DCE in human plasma, and it can readily be used for clinical pharmacokinetic studies and routine monitoring of IF-treated patients in a hospital setting.

Metabolism and pharmacokinetics of oxazaphosphorines

The 2 most commonly used oxazaphosphorines are cyclophosphamide and ifosfamide, although other bifunctional mustard analogues continue to be investigated. The pharmacology of these agents is determined by their metabolism, since the parent drug is relatively inactive. For cyclophosphamide, elimination of the parent compound is by activation to the 4-hydroxy metabolite, although other minor pathways of inactivation also play a role. Ifosfamide is inactivated to a greater degree by dechloroethylation reactions. More robust assay methods for the 4-hydroxy metabolites may reveal more about the clinical pharmacology of these drugs, but at present the best pharmacodynamic data indicate an inverse relationship between plasma concentration of parent drug and either toxicity or antitumour effect. The metabolism of cyclophosphamide is of particular relevance in the application of high dose chemotherapy. The activation pathway of metabolism is saturable, such that at higher doses (greater than 2 to 4 g/m2) a greater proportion of the drug is eliminated as inactive metabolites. However, both cyclophosphamide and ifosfamide also act to induce their own metabolism. Since most high dose regimens require a continuous infusion or divided doses over several days, saturation of metabolism may be compensated for, in part, by auto-induction. Although a quantitative distinction may be made between the cytochrome P450 isoforms responsible for the activating 4-hydroxylation reaction and those which mediate the dechloroethylation reactions, selective induction of the activation pathway, or inhibition of the inactivating pathway, has not been demonstrated clinically. Mathematical models to describe and predict the relative contributions of saturation and autoinduction to the net activation of cyclophosphamide have been developed. However, these require careful validation and may not be applicable outside the exact regimen in which they were derived. A further complication is the chiral nature of these 2 drugs, with some suggestion that one enantiomer may have a favourable profile of metabolism over the other. That the oxazaphosphorines continue to be the subject of intensive investigation over 30 years after their introduction into clinical practice is partly because of their antitumour activity. Further advances in analytical and molecular pharmacological techniques may further optimise their use and allow rational design of more selective analogues.

Ifosfamide in the elderly: clinical considerations for a better drug management

The therapeutic strategy used for elderly affected by malignant neoplasms should take into account the common variables present in oncological patients, and the specific alteration of the elderly metabolism and their possible morbidity. Ifosfamide is an active drug for various tumors with elevated incidence in the elderly. We analyze the principle criteria in the selection of these patients and the alterations of metabolism which correlates to aging with their consequences on the pharmacokinetics of ifosfamide. Finally, we propose clinical guidelines to optimize the use of ifosfamide in elderly patients affected by malignant tumors.

Phase II trial of first-line high-dose ifosfamide in advanced soft tissue sarcomas of the adult: a study of the Spanish Group for Research on Sarcomas (GEIS)

BACKGROUND

The agent Ifosfamide (IFOS) is active against soft tissue sarcomas (STS), and patients who progress to IFOS at doses < or = 10 g/m2 show remissions when exposed to high-dose ifosfamide (HDI) (i.e., doses > 10 g/m2), which supports a dose-response relationship for this drug. Because of a lack of first-line studies in adult STS patients, we decided to test the activity and toxicity of HDI in a phase II trial.

PATIENTS AND METHODS

Forty-eight patients were enrolled in the study. IFOS was administered at a dose of 14 g/m2 by continuous infusion over six days every four weeks. Granulocyte-macrophage colony-stimulating factor (GM-CSF) at 5 micrograms/kg/day for 10 consecutive days was systematically administered after an episode of neutropenic fever or a delay in hematologic recovery. Patients were treated until progression or the occurrence of severe toxicity, and surgical rescue was attempted when possible.

RESULTS

Six pathology-established complete remissions and 11 partial remissions were observed in 45 assessable patients with a response rate of 37.7% (95% CI: 25.5%-50%). Grade 3-4 toxicity (% of cycles) was noted by hemoglobin (17%), leukocyte (75%), granulocyte (75%) and platelet (13%) counts in 158 evaluable cycles. GM-CSF was administered to 28 patients, and 25 suffered one or more episodes of neutropenic fever. Renal toxicity was mild and reversible with some degree of tubular and glomerular dysfunction detected in up to 60% of patients. Grade 3 CNS toxicity was observed in 32% of patients but only one required interruption of therapy. Sixty-four per cent of the patients had asthenia grade 2-3 and 20% were excluded from the study due to excessive toxicity. There was one treatment-related death.

CONCLUSIONS

HDI is an active drug in first-line therapy against adult STS. Different administration schedules should be evaluated in an attempt to improve its therapeutic index.

Ifosfamide plus cisplatin as primary chemotherapy of advanced ovarian cancer

We have performed a phase II study to evaluate the activity and toxicity of ifosfamide and cisplatin as first-line treatment for advanced ovarian cancer. Patients were treated with cisplatin 100 mg/m2 on day 1 and ifosfamide 5 g/m2 in 18-hr continuous infusion on day 1 or 1.5 g/m2 bolus on days 1-5. Between August 1988 and March 1990, 30 women were entered in the trial, 26 of them with measurable disease. The overall clinical response rate was 69% (95% CI: 48-85%), including 34.6% complete responses (95% CI:17-55%). Reassessment laparotomy was performed in 12 cases, and 4 (33%) exhibited a pathologic complete response. For all patients, the median duration of progression-free survival was 14 months, and the median overall survival was 25 months. There were no major differences in the response rate or survival between the two ifosfamide administration modalities. Relevant toxicities were grade IV hematologic toxicity in 11/30 patients and grade IV renal toxicity in 2/30 patients. A patient with grade IV encephalopathy developed a trauma-related cerebral hemorrhage and died 2 months later. The combination of ifosfamide and cisplatin is active in first-line therapy in advanced ovarian cancer, although it does not seem to improve the efficacy or toxicity profile of conventional combinations.

Ifosfamide nephrotoxicity: limited influence of metabolism and mode of administration during repeated therapy in paediatrics

This study investigated the relationship between both acute and chronic nephrotoxic effects of ifosfamide (IFO) and its metabolism. 15 paediatric patients (4 girls) were investigated. Each received 6-9 g/m2 IFO over 15 days, repeated every 3 weeks for up to 16 courses. The pharmacokinetics and metabolism of IFO were measured during its administration, either as a continuous 72 h infusion or as three bolus doses of 3 g/m2 on consecutive days. In 8 patients, the metabolism of IFO was investigated during one early course and one late course to determine the magnitude of any changes following repeated administration. Acute measures of renal toxicity were not correlated with any of the IFO pharmacokinetic or metabolic parameters in the same course, whether the drug was administered as a bolus or by continuous infusion. Chronic renal toxicity, determined 1 month (n = 13) or 6 months (n = 8) after treatment, did not correlate with any of the IFO pharmacokinetic or metabolic parameters in any individual course of treatment. The overall degree of nephrotoxicity, however, was correlated with the changes in metabolism between late and early courses (n = 8). There was a negative correlation between the change in area under the curve of the dechloroethylated metabolites of IFO and the overall nephrotoxicity at 1 month or 6 months after treatment (both r2 = 0.66, P = 0.014). The results imply that patients in whom metabolism via dechloroethylation decreases are at a greater risk of chronic nephrotoxicity. This is contrary to the hypothesis that the systemic production of chloroacetaldehyde is the mechanism by which IFO causes nephrotoxicity. The importance of acute and chronic changes in renal function for long-term outcome remains to be determined.

The anti-tumour activity of ifosfamide on heterotransplanted testicular cancer cell lines remains unaltered by the uroprotector mesna

Ifosfamide is clinically used in combination chemotherapy regimens for the treatment of patients with high-grade lymphomas, sarcomas and metastatic germ cell tumours. In order to reduce the oxazophosphorine-related urothelial toxicity, sodium mercaptoethane sulphonate (mesna) is used in different schedules following the administration of ifosfamide. The proposed mechanism of mesna activity is the binding of toxic oxazaphosphorine metabolites such as acrolein in the urine of the patients. Since an influence of mesna on ifosfamide anti-tumour activity is controversial, the current study has used xenografts from two human testicular cancer cell lines heterotransplanted into nude mice to study the anti-tumour activity of ifosfamide in combination with different dosages and schedules of mesna. In both human testicular cancer cell lines, H 12.1 and 2102 EP, ifosfamide demonstrated anti-tumour activity as a single agent. No reduction in ifosfamide activity was observed with the application of mesna at a dose range from 50% to 200% of the ifosfamide dose. Furthermore, the application of mesna before and 3 h after ifosfamide, a schedule used in many clinical protocols because of the short half life of mesna, not only maintained high ifosfamide anti-tumour activity but also seemed to be associated with the lower systemic and urothelial toxicity of ifosfamide therapy compared with ifosfamide given alone. In conclusion, the experimental in vivo system using human heterotransplanted testicular cancer cell lines confirms the significant anti-tumour activity of ifosfamide in malignant germ cell tumours and demonstrates that mesna does not impair ifosfamide anti-tumour activity in this model. These results are most likely transferable to the use of mesna in patients with metastatic testicular cancer.

Prophylaxis and reversal of ifosfamide encephalopathy with methylene-blue

The antineoplastic ifosfamide produces dose-dependent signs of neurotoxicity. After ifosfamide overdose in a patient, we found excessive urinary excretion of glutaric acid and sarcosine, which is compatible with glutaric aciduria type II, a defect in mitochondrial fatty acid oxidation that results from defective electron transfer to flavoproteins. We therefore used the electron-accepting drug methylene-blue as an antidote for ifosfamide encephalopathy. In one patient, ifosfamide neurotoxicity was rapidly reversed by methylene-blue 50 mg intravenously. In another patient with previous episodes of ifosfamide encephalopathy, methylene-blue was administered orally prophylactically. No symptoms of neurotoxicity were noted.

Depletion of total cysteine, glutathione, and homocysteine in plasma by ifosfamide/mesna therapy

The sulfhydryl status of cells, particularly the intracellular concentration of glutathione, is a critical determinant of the response of tumor and normal cells to cytostatic drugs. Recent data indicate that the administration of mercaptoethane sulfonate (mesna), which is often combined with ifosfamide, markedly decreases the circulating concentration of total cysteine and could thereby influence the response of the organism to the cytotoxic effects of chemotherapy. The aim of the present study was to assess the effects of the combination of ifosfamide/mesna on sulfhydryl and disulfide homeostasis in tumor patients. Ifosfamide was infused into 14 patients with advanced sarcoma for 5 days at a dose of 2.4-3.2 g/m2 per day together with mesna. The plasma concentrations of total mesna, cysteine, glutathione, and homocysteine were measured before and on days 1 and 6 of the first course of ifosfamide/mesna therapy and prior to the next course of chemotherapy, and the urinary excretion of cysteine and mesna was monitored daily using a high-performance liquid chromatography (HPLC) method. Ifosfamide/mesna resulted in a marked depletion of circulating total cysteine, i.e., cysteine, cystine, and cysteine mixed disulfides [from 245 +/- 36 to 50 +/- 14 nmol/ml (mean +/- 95% CI) on day 6], total glutathione (from 6.9 +/- 1.1 to 2.5 +/- 1.1 nmol/ml), and total homocysteine (from 12.3 +/- 2.1 to 1.4 +/- 1.1 nmol/ml). The values returned to baseline levels prior to the next course of chemotherapy. The urinary excretion of cysteine increased significantly from 0.28 to 1.82 mmol/day on the 1st day, whereupon it returned toward baseline. An average of 62% +/- 6% of the delivered dose of mesna was recovered in urine. The combination of ifosfamide/mesna results in depletion of circulating total cysteine, glutathione, and homocysteine. This marked derangement of sulfhydryl and disulfide homeostasis could modulate the efficacy and toxicity of ifosfamide/mesna therapy.

Results of chemotherapy using ifosfamide with doxorubicin in advanced breast cancer

Ifosfamide has single agent activity in advanced breast cancer and may potentiate the activity of doxorubicin. The combination of ifosfamide 5 g/m2 and doxorubicin 40 mg/m2 every 3 weeks for 4 cycles was used to treat 77 patients with advanced breast cancer. Fifty three patients had not received prior chemotherapy. All patients had one or more poor prognostic features, including tumor expression of epidermal growth factor receptor in 11/12 tested. The overall response rate was 74% (95% confidence intervals 62%-83%). The median survival was 9.4 months. The principal toxicities were febrile neutropenia and ifosfamide encephalopathy each in 6% of patients. A high percentage of the projected dose intensity was administered. This is a highly active combination with acceptable toxicity in advanced breast cancer, although the long term survival remains poor. Further exploration of ifosfamide in combination chemotherapy for advanced breast cancer is warranted.